The injection of therapeutic agents in hospital, clinic, and home-based settings is a common procedure, but can sometimes be complex and difficult to perform, even for experienced healthcare providers. Drawing a therapeutic agent into a syringe and injecting it into a patient requires a certain level of manual dexterity and strength, in addition to sufficient visual and mental acuity to perform the procedural steps. The risk of needlestick injury also exists throughout all of the steps of a manual injection procedure. In home-based settings, these challenges could lead to reduced patient compliance with treatment regimens.
Nevertheless, as reliance upon home-based injection regimens continues to expand, the challenges with syringe injection have become more diversified. For example, patients with physical or cognitive impairment may need to perform such injections, without assistance from in-home care providers. Also, some injections require more force than users are capable of delivering, for instance if the injected substance has a high viscosity. Furthermore, for some medications, the injection process can cause discomfort related to the rate of injection. In some instances, a user may want to increase the rate of injection, in order to accomplish the injection in a shorter time, or may want to decrease the rate of injection or stop the injection, for example to mitigate injection-related pain. There is therefore a need for a power-assisted injection device, which allows the user to both control a stored energy source and also provide some amount of user supplied power to the injection, and thus increase or decrease the injection rate, or stop the injection, at will.